If you know how to change the options on the profile's main page, then you should know how to do this. Say you were going to change the option "Humor" to brawl friend code. Im not sure what the exact option is to do this, but change it to Brawl FC for example. Then check the box that says "Display on posts" and "Obligatory for the registration"

great news! I figured out how to add those things to the profile editor and I'm gonna experiment with it. Now that I can do this I plan to greatly increas the profile customization capabilities! Thanks for the great suggestion paradox, your voice will always be heard here at nbn